The invention relates to a measuring apparatus for measuring the cloth tension in a weaving machine and to a weaving machine with at least one measuring apparatus of this kind. Furthermore, the invention relates to a weaving machine with two warp beams, which is equipped with at least one measuring apparatus each for the measurement of the cloth tension for each warp beam.
In weaving machines the warp let-off must be regulated in such a manner that the warp tension is held constant independently of the diameter of the warp beam. For this purpose the warp tension was previously measured directly. The warp tension can however also be determined indirectly from measurements of the cloth tension. The specifications DE 39 05 881 C2 and EP 0 385 061 B2 describe “warp tension measurement devices” in which the cloth tension is measured by means of a measuring apparatus which is inserted into the breast beam. The Japanese laying-open print JP 2-293444 discloses a measuring apparatus for the measurement of the cloth tension in or at the breast beam for the precise determination of the warp thread tension. In a first embodiment a load cell is let into the breast beam. In a second embodiment the breast beam is rotatably journalled and the contact pressure force on the breast beam is transmitted to one or more load cells which are in connection with the breast beam. The Japanese laying-open print JP 2-307938 describes a measuring apparatus which is secured to the breast beam and measures the cloth tension between the cloth edge and the breast beam.
All of the above-mentioned measuring apparatuses for measuring the cloth tension from the prior art are firmly connected to the breast beam. This is considered disadvantageous since these solutions are not very flexible. Since the cloth tension is not constant over the width of the cloth (it is the greatest in the middle and decreases significantly in the direction towards the weaving edges), it is necessary in certain cases, with different cloth widths, to adapt the position of the measuring apparatus for measuring the cloth tension in the width, i.e. transversely to the direction of travel of the cloth. This holds in particular for weaving machines in which the draw in is asymmetric, i.e. is carried out with one-sided width variation of the warp draw in width and/or of the cloth width respectively. A simple adaptation of the measurement position transversely to the direction of travel of the cloth is however not possible with the mentioned measuring apparatuses from the prior art. In this regard, double beam weaving machines present a special problem. Not only must the warp tension for each warp beam be measured individually and held constant, but the warp tensions of the two warp beams must also be of exactly equal magnitude.